Hydrochlorination process for
recovery of metal values



United States Patent Matter enclosed in heavy brackets appears in theoriginal patent hut forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE The present invention relates to a novelhydrochlorination process for winning molybdenum, tin, antimony, bismuthand like metal values from their ores and minerals. In the presentprocess, a metal value containing source material, containing one ormore of molybdenum, tin, antimony, bismuth and the like metal values,the chloride compounds of which readily are volatizable, is contactedwith hydrogen chloride and an oxidizing gas at a tempera turesufficiently high that the metal values are converted to volatilechloride compounds and removed from the reaction zone whilesimultaneously assuring that impurity metal values remain as a solidresidue of oxides which are substantially non-volatile under the processtemperatures.

This application is a continuation-in-part of application Ser. No.237,739, filed Nov. 14, 1962 and now abandoned.

This invention relates to ore processing and more particularly isconcerned with a novel hydrochlorination process for winning certainmetal values from their ores and minerals.

Although large reserves of ores containing molybdenum, tin, antimony,bismuth and the like metal values are both commercially and technicallyimportant to the metals industry are known, in many instances these oresare in a form such that they do not lend themselves to ready recover ofthe metal values therefrom in high purity by conventional ore treatingprocesses. This can be illustrated in the winning of molybdenum valuesfrom oxidized molybdenum-containing ores contaminated with iron.

Oxidized molybdenum-containing minerals frequently are found togetherwith molybdenite (MoS the mineral presently used for major commercialmolybdenum production. However, although these oxidized minerals providea potential large source of molybdenum, the molybdenum cannot beconcentrated in or separated from such oxidized minerals by the low-costfroth flotation technique which works very efliciently on molybdenitcand other molybdenum sulfides.

Several concentration processes, e.g. special flotation techniques,magnetic separation and leaching procedures have been proposedheretofore for these oxidized ores but none have been economicallysuccessful. Additionally, attempts have been made to upgrade molybdenumconcentrates by the use of chlorination techniques whereby impuritiesaer removed as soluble chlorides (British Patent 859,263). BritishPatent 374,250 reports the use of chlorine in the presence of a reducingagent to recover molybdenum from M05 (molybdenite) ores, but thisprocess allegedly results in excessive chlorine consumption by iron andother gangue minerals, lower recoveries of metal val- Re. 26,982Reissued Nov. 17, 1970 ues and as indicated hereinbefore is notapplicable with certain oxide ores.

It is a principal object of the present invention to provide a processfor recovering metal values in high yields from ores and mineralswherein the recovered metal products as produced are of high purity.

It is another object of the present invention to provide a novelhydrochlorination process for winning metals from oxidized ores by whichprocess the resulting chloride containing metal product is readilyseparated from the reaction mass.

It is an additional object of the present invention to provide a novelhydrochlorination metal winning process having low losses of chloridevalues which also provides for ready recycle of the chlorinatingreactant.

It is a further object of the present invention to provide a novel metalwinning process that is carried out at relatively low temperatures.

It is still another object of the present invention to provide a novelprocess for recovering metal values from ores which are not suitable fortreatment by traditional flotation concentration techniques.

A further object of the present invention is to provide a novel processfor treating ores and concentrates to separate molybdenum, tin, antimonyor bismuth values from iron, tungsten, or lead impurities containedtherein.

A particular object of the instant invention is to provide aneconomical, successful novel process for the production of essentiallyiron-free molybdenum values from iron-containing molybdenum ores andconcentrates.

These and other objects and advantages readily will become apparent fromthe detailed description presented hereinafter.

In the present process, a metal value containing source material; e.g.an ore or mineral containing one or more of molybdenum, tin, antimony,bismuth and the like metal values the chloride compounds of whichreadily are volatilizable, is contacted with hydrogen chloride and anoxidizing gas, e.g. air or oxygen, at a temperature sufliciently highthat the metal values are converted to volatile chloride compounds andremoved from the reaction Zone while simultaneously assuring thatimpurity metal values such as iron, tungsten, calcium, magnesium andlead, for example, remain as a solid residue of oxides which aresubstantially non-volatile under the process temperature. The volatilemetal chlorides ordinarily are recovered by condensation afterseparation from the reaction mass.

More particularly in the instant process an ore containing metal valueshaving volatile chlorides is contacted with hydrogen chloride and oxygenor air, either sequentially or as a hydrogen chloride-oxygen mixture orhydrogen chloride-air mixture at a temperature of from about 400 toabout 800 C., preferably at from about 500 to about 700 C. for a periodof time sufficient to prepare volatile chlorides of the metal values.The volatile metal value chlorides are removed from the reaction mass.These are recovered, ordinarily by condensation, at a temperature belowtheir sublimation point.

The recovered metal chlorides can be used as produced. Alternatively, ifdesired, these compounds can be converted to the corressponding oxideswith subsequent recovery of regenerated hydrogen chloride. This lattermaterial can be recycled for reaction with additional ore.

The amount of hydrogen chloride to be employed is not critical exceptthat the minimum total chloride value must be sufficient to provide forthe desired degree of conversion of the metal values in the ore ormineral source which form volatile oxychlorides.

The amount of oxygen or air to be used at a minimum should assurecomplete reaction with and oxidation of impurity metal values tonon-volatile oxide forms. The maximum quantity of oxidizing gas is notcritical except that when mixtures of this material with hydrogenchloride are used the mixtures should not be excessively dilute withrespect to the hydrogen chloride. Generally, with the mixtures ahydrogen chloride/air or oxygen volume proportion of from about 1/1 toabout U6 is used.

Ordinarily, the ore particles are contacted with a mixture of hydrogenchloride and oxygen or hydrogen chloride and air. However, use of themixtures is not essential unless one or more of the impurity metalstends to form a volatile chloride compound in the absence of oxygen orwater at the temperature and hydrogen chloride concentration required toconvert the metal values to volatile chloride compounds. For example, ifiron is present only in the ferrous state and as the sole importantimpurity, the treatment with hydrogen chloride can precede the treatmentwith air. Although this will result in an initial chloride retention bythe iron through formation of ferrous chloride, this is only temporaryand the chloride is recovered during the subsequent oxidation step,either as chloride or, if moisture is present as hydrogen chloride.Similarly, if ferric iron is present treatment of the reaction mass withhydrogen chloride in the absence of water or air will produce ferricchloride which tends to evolve along with the product. This undesirableevolution can be suppressed, however, by using moist hydrogen chloridesince ferric chloride readily is converted by water to hydrogen chlorideand ferric oxide at temperatures above about 400 C. Thus, some oresfirst can be contacted with oxygen and then with moist hydrogenchloride, particularly in a batch type operation. For continuousoperation, the greater simplicity and economy of co-treatment withhydrogen chloride and air is highly preferable.

It does not matter whether the hydrogen chloride required forvolatilization of the metal value chloride compounds is supplied to theore body as such or is generated in situ by, for example, the hydrolysisof a metal halide such as ferric chloride.

The particulation of the ore for use in the present process is notcritical as both finely divided, e.g. 100 200 mesh or finer U.S. sieveseries, materials and relatively coarse screenings (e.g. up to 0.125inch or larger in diameter) are opened by the instant process.

The process is particularly suitable for recovering molybdenum valuesfrom oxidied molybdenum ores or mixed molybdenum oxide-sulfide oreswhich cannot be concentrated or treated by traditional froth flotationtechniques or other conventional methods.

With these molybdenum ores, the ore is contacted with hydrogen chlorideand oxygen or air, sequentially or as hydrogen chloride-air or hydrogenchlorideoxygen mix tures, at a temperature of from about 400 to about800 C., preferably from about 500 to about 700 C., for a period of fromabout minutes to about an hour or more and preferably from about 7minutes to about 30 minutes. Ordinarily the hydrogen chloride/molybdenumweight proportions, expressed as Cl/Mo, based on the total molybdenumconcentration in the ore mass employed ranges from about 0.75 to about 5pounds chloride/pound of molybdenum. The volatile product molybdenumchloride compounds are removed from the reaction mass and recovered bycondensing these at a temperature below their sublimation point, usuallyat from about 100 to about 150 C. and preferably at from about 110 toabout 120 C.

At reaction temperatures greater than about 400 C. in the presence ofair, the reaction of HCl with iron oxide-a common contaminant inmolybdenum-containing ores-to form the related ferric chloride isthermodynamically not favored while the formation of molybdenumoxychlorides and their volatilization from the reaction mass is highlyfavored. At these temperatures,

therefore, not only is the reaction of HCl with molybdenum oxide-sulfidemixed ores promoted but also excessive loss of chlorine values to ganguematerials, such as iron, is substantially completely eliminated.

If the condenser tube for product recovery is cooled to a temperaturebelow about C., the molybdenum oxychlorides condense as a relativelycompact cake because of the presence of co-condensed water. This cakeclings tenaciously to the wall of the condenser and is somewhatdifficult to remove therefrom. However, by maintaining the temperatureof the condenser between about 100 and 150 C., and, preferably fromabout to about C., the molybdenum oxychloride condenses as a loose,powdery solid material that readily is re moved from the condenser andseparated from the exit gas stream.

With oxidic molybdenum ores, for example, such as molybdite,ferromolybdate and powellite as well as more variable minerals such asparosites and iron oxides con taining small amounts of molybdenum withintheir mineral structure, both the molybdenum content of the ore and thechloride content of the hydrogen chloride reagent are recovered in theproduct to a high degree and the chloride readily is converted tohydrogen chloride for re-use. With sulfide-containing ores, highrecoveries of the molybdenum can still be obtained if operatingtemperatures sutficiently high (i.e., above about 500) are employed.However, chloride compounds of sulfur are co-produced and these resultin some chloride losses. Consequently, it is preferable to pre-roastsulfide-containing ores with air alone before introducing the hydrogenchloride. In general, a roasting period of about one hour or more at atemperature of about 500-700" is sufficient.

The instant process can be carried out in batch, cyclic or continuousoperations. Conveniently an integrated batch-type operation is usedwherein the gaseous reactant hydrochlorination agent is passed through aheated bed or column of the oxidized ore. The exit gases then can becooled to separate the molybdenum oxychloride products therefrom.

Reactors, transfer lines, product receivers and the like are to be ofmaterials and of a design so as to be structurally sound at the reactiontemperature and not detrimentally attacked by the reactants and/orproducts.

The following examples will serve further to illustrate the presentinvention but are not meant to limit it thereto.

EXAMPLE 1 A mixed oxide-sulfide molybdenum ore was crushed to passthrough a No. 8 mesh US. Standard Sieve. About 40 grams of the ore wasplaced into a vertical glass reactor tube having an inside diameter ofabout 1 inch and about 12 inches long. The tube and contents were heatedto about 500 C. by means of an electric resistance coil. A mixture ofhydrogen chloride and air (1:1.5 HCl/ air) at a flow rate of about .033gram/minute was passed up through the tube for a period of about thirtyminutes during which period the reactor tube was continuously vibratedso as to prevent channeling of the gas flow through the reactor. Thisprovided an equivalent Cl/Mo weight proportion of 0.4 gm. Cl/0.12 gm. M0or 3.3/1.

The exit gases from the top of the reactor were passed into an aircooled tube whereupon the volatilized molybdenum oxychloride productscondensed at a temperature of about 110 C. The results of this run aresummarized in Table I which follows.

EXAMPLE 2 A number of runs were made using a sample of a high ironmagnetic molybdenum concentrate containing 0.895 percent molybdenum, asoxide, and 0.016 percent molybdenum as sulfide. For these runs, the gamegeneral procedure and apparatus as described in Example l was employed.

In each study, about 50 grams of the concentrate was heated to apredetermined temperature and reacted with approximately 2.1 grams ofanhydrous hydrogen chloride (equivalent to about 5 lb. Cl/l lb. Mo) overa 30 minute reaction period. Following this step, the system wasmaintained at the predetermined temperature for a period of from aboutto about 20 minutes while passing moist air through the ore bed to purgeexcess reagents and effect substantially complete separation of themolybdenum chlorides from residual iron oxides. Table II presents theresults obtained at a number of prededetermined temperatures.

At temperatures below about 400 C., considerable FeCl was Volatilizedwith the molybdenum oxychlorides as determined by visual observation andthe color of the condensed product. However, in the presence of the airthis quantity decreased with increasing temperature until at 600 C.essentially no iron was noted in the condensed product, despite the highiron content of the feed. These results also show the effect ofincreasing temperature on molybdenum recovery as well as on chlorideloss in the non-volatile residue. This loss primarily is attributed toconsumption of hydrogen chloride in the formation of ferrous chloride.

EXAMPLE 3 The reactor and procedure described for Example 1 was usedwith a low grade molybdenum ore contaminated with considerable amountsof iron. This ore upon analysis was found to contain 0.368 percentmolybdenum (as oxide), 0.117 percent molybdenum (as sulfide), 2.0percent iron and 1.0 percent sulfur.

About 100 grams of the ore was placed in the reactor and heated to 600C. after which time a 1/1 volume mixture of air and hydrogen chloridewas introduced into the reactor for a period of about minutes whilemaintaining the temperature. This provided for a total hydrogen chloridegas flow of 1.2 grams (equivalent to about 2.5 lb. Cl/l lb. M0). Thevolatile product was condensed in a tube maintained at a temperature offrom about 110 to 120 C. This product, as formed, was a loose powderysolid which readily was removed from the condenser tube.

Analysis of the residue in the reactor and the condensed Volatilizedproduct are summarized as follows.

Residue: Percent Mo (as oxide) 0.072 Mo (as sulfide) 0.010 Cl 0.018 S0.31

Volatilized product:

Al 0.007 Bi 0.2 Cu 0.003 Fe 0.02 Pb 0.005 Si 0.06

The product, which contained 83% of the molybdenum in the ore, containedless than 0.3% total impurities.

EXAMPLE 4 One gram of M00 was mixed with 2 grams of about 1:1 Fe O Fe Oand 200 grams of silica sand and the resulting mixture placed on aporous support in the reactor tube described in Example 1. The mixturewas heated to about 450 and air which had been bubbled through 12 Naqueous HCl was introduced into the reactor tube through the bottom.Almost immediately white molybdenum oxychloride was evolved from thereaction mass. Volatilization was complete after 15 minutes of contactwith the air:wet hydrogen chloride mixture at the reaction temperature.The condensed product was substantially free from iron.

EXAMPLE 5 In the manner of Example 1, a quantity of low-grade antimonyore containing 2.88% Sb and 0.76% Fe after crushing to 28 mesh andcontacting with air and hydrogen chloride at 450 C. for 10 minutes usinga 1/1 HCl/air volume ratio and a chloride concentration sulficient toreact with the antimony values effected a 94.5% recovery of the antimonyas volatile oxychloride essentially free of iron contamination.

EXAMPLE 6 In the manner of Example 1, a mixed pre-roasted oxidesulfideore of molybdenum containing 0.10% vanadiumsulfides and 0.32% leadsulfides can be contacted at 550 with a hydrogen chloride-air mixture(l/l HCl/air volume proportions) for about 30 minutes and a volatilemolybdenum oxychloride product taken off. The product is free ofvanadium but includes about 1.5% of lead. The process can be repeated.using the lead containing product as the starting material, and a finalmolybdenum oxide product containing less than 0.003% Pb can be obtainedin good yield. based on the molybdenum content of the original ore.

EXAMPLE 7 In the manner of Example 1. efiicient separation of a numberof metal value containing mixtures is achieved J by treatment ofcorresponding ores or minerals with hy- Overhead products consisting ofvolatile chloride compounds Non-volatile oxides present in residues (a)Bismuth Iron and lead. (b) Tin Iron.

Iron, lead and (c) Tin vanadium. (d) Antimony and molybdenum Lead andvanadium. (e) Tin and molybdenum Lead. (f) Tin and antimony Iron.

Various modifications can be made in the present process withoutdeparting from the spirit or scope thereof for it is understood that welimit ourselves only as defined in the appended claims.

We claim:

1. A process for recovering metal values from oxidized ore and mineralsource materials which comprises:

(a) providing a metal value containing source material containing atleast one member selected from the group consisting of molybdenum, tin,antimony and bismuth, and also containing oxide forming [oxidizableimpurities] impurity metal values selected from the group consisting ofiron, vanadium, tungsten, aluminum, magnesium, zinc, copper, calcium,lead and silicon,

(b) contacting a particulated form of said metal value containing sourcematerial at a temperature of from about 400 to about 800 C. withhydrogen chloride and an oxidizing gas selected from the groupconsisting of air and oxygen at a hydrogen chloride/ metal valueproportion at least suflicient to provide volatile chlorides of saidmetal values, and [at an] in the embodiment of the process involvingcontacting with a mixture of oxidizing gas and hydrogen chloride, theoxdizing gas/hydrogen chloride proportion is at least sufficient toassure substantially complete and selective oxidation of said impuritymetal values to non-volatile oxide forms,

(c) removing the resulting volatile metal chloride compounds from thereaction mass while maintaining the temperature within the range of fromabout 400 to about 800 C., and

(d) recovering said volatile metal chlorides.

2. The process as defined in claim 1 wherein the metal value containingsource material is a molybdenum ore, and, including the steps ofcontacting said ore for a period of from about 5 minutes to about 1 hourat a temperature of from about 400 to about 800 C. with hydrogenchloride and a member selected from the group consisting of oxygen orair at a hydrogen chloride/molybdenum proportion, expressed as Cl/Mo, offrom about 0.75 to about 5 pounds Cl/l pound of Mo, separating theresulting volatile molybdenum chloride compounds from the residualreaction mass and condensing the volatile molybdenum chloride compoundsat a temperature of from about 100 to about 150 C.

3. The process as defined in claim 2 wherein the reaction between thehydrogen chloride and molybdenum 8 ore is carried out at a temperaturebetween about 500 to about 700 C. for a period of from about 7 to about30 minutes and the separated volatile molybdenum chloride compounds arerecovered by condensing these at a temperature of from about to about C.

4. The process as defined in claim 2 wherein the hydrogen chloride andoxidizing gas are employed as a mixture having a hydrogenchloride/oxidizing gas volume proportion ranging from about 1/1 to about1/6.

5. The process as defined in claim 1 and including the step ofconverting the recovered volatile metal choride compound products to thecorresponding oxide and recovering regenerated hydrogen chloride.

[6. The process as defined in claim 1 wherein the oxide formingoxidizable impurities are selected from the group consisting of iron,vanadium, tungsten, aluminum, magnesium, zinc, copper, calcium, lead andsilicon] References Cited The following references, cited by theExaminer, are of record in the patented file of this patent or theoriginal patent.

UNITED STATES PATENTS 1,329,380 2/1920 Doerner 23-17 1,481,697 1/1924Dyson et al. 23-17 1,911,505 5/1933 Herold et al 23-17 1,974,280 11/1934Mitchell 23-87 2,330,114 9/1964 .lahn 23-219 3,148,941 9/ 1964 Gens.

HERBERT T. CARTER, Primary Examiner U.S. Cl. X.R. 2387, 98,

